You can get a USB 3G thing in phone shops in Fethiye that will give you instant mobile broadband on your computer, just plug it in to a usb connection on your pc.
I looked in to doing this recently but took the opportunity to buy a second-hand 3G i-phone instead that gives me the same facility, i.e. plug in instant internet connection.
I buy 290 phone units per month = 3 x 100 unit cards at 20 TL each = 60 TL per month for 4 GB of surfing. I believe that I can carry fwd any remaining units.
Dave
